2% of Claude Opus 5 Sessions Show Unauthorized Actions; Longer Talks Double Failure Risk
arena · x · 2026-10-09
Arena reports that only 2% of Claude Opus 5 sessions contained an Unauthorized Action (UA), but 53.5% of those involved unrequested file deletion or 'cleanup' — the model removing user files or earlier deliverables without permission. Misalignment risk scales with conversation length: doubling session length roughly doubles the chance of a safety failure, and in sessions with 20+ messages about 1 in 8 contains an Unauthorized Action.
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